Alkylation process



United States Patent ALKYLATION PROCESS Herbert C. Brown, WestLafayette, and Willard S. Higley, Hammond, Ind., assignors to StandardOil Company,

Chicago, 11]., a corporation of Indiana a This invention relates to aprocess for the alkylation of alkylatable aromatic compounds withalkylating agents containing at least three carbon atoms in thealkylating group in the presence of catalytic proportions of phosphoruspentafiuoride.

One object of this invention is to provide novel catalysts for thealkylation of alkylatable aromatic compounds with alkylating agentscontaining at least three carbon atoms in the entering (alkylating)group. Another object is to provide a process for the alkylation ofaromatic hydrocarbons having at least one alkylatable nuclear carbonatom with an alkylating agent containing at least three carbons in thealkylating group in the presence of PFs or a material furnishing PFsunder the alkylation reaction conditions. An additional object is toprovide a process for the alkylation of aromatic hydrocarbons having atleast one alkylatable nuclear carbon atom with a monoolefinichydrocarbon containing at least three carbon atoms per molecule in thepresence of PF5. A further object is to provide a process for theselective alkylation of alkylatable aromatic hydrocarbons with aterminal vinyl olefin containing at least three carbon atoms permolecule in the presence of ethylene. These and other objects of ourinvention will become apparent fiom the ensuing description thereof.

We have discovered that PFs, or materials which furnish PF5, in thealkylation zone under the conditions of the alkylation reaction, such asbenzenediazonium hexafluorophosphate, function as catalysts for thealkylation of alkylatable aromatic compounds with olefinic hydrocarbonsor other alkylating agents containing at least three carbon atoms permolecule. Since the alkylation process of this invention is broadlyapplicable to a large variety of aromatic compounds and alkylatingreagents containing at least three carbon atoms in the alkylating group,the preferred reaction conditions cannot be indicated for each possibleinstance of the application of this invention; these are, however,readily determinable by simple small-scale routine experimentation.

The alkylation process of the present invention may be practiced with avariety of aromatic compounds such as alkylatable aromatic hydrocarbonsor alkylatable derivatives of aromatic hydrocarbons, for example,substitution products such as halogen-, hydroxy, alkoxy-, or othersubstitution derivatives of aromatic hydrocarbons. Specific exampleswhich are supplied for purposes of illustration but not as limitationsinclude monocyclic aromatic hydrocarbons containing at least onealkylatable nuclear carbon atom, for. example, benzene, toluene, theisomeric xylenes, ethylbenzene, n-propylbenzene, isopropylbenzene, theethyl toluenes, the ethyl xylenes, pseudocumene, hemimellitene,sec-butylbenzene, tbutylbenzene, isodurene, diethylbenzenes, prehnitene,isoamylbenzene or the like. Examples of dicyclic aromatic hydrocarbonscontaining an alkylatable nuclear carbon atom comprise tetralin,naphthalene; alkyl naphthalenes, such as l-methylnaphthalene,2-methylnaphthalene, l-isopro- Patented Oct. 16, 1956 pylnaphthalene,2-ethylnaphthalene, 2,6-dimethylnaphthalene, isopropylnaphthalene, andthe like; diphenyl, alkyl-substituted diphenyls; indene, alkylindenes,dihydroindenes and the like. The alkylation process of this inventionmay also be applied to tricyclic aromatic hydrocarbons such asanthracene, alkyl anthracenes, phenanthrene and even to alkylatablearomatic hydrocarbons containing more than three rings. Examples ofalkylatable aromatic compounds (which may be considered as derivativesof aromatic hydrocarbons) include various phenolic compounds, such asphenol, pyrocatechol, resorcinol, hydroquinone, pyrogallol; phenolicethers such as phenetole, anisole, phenyl t-butyl ether and the like.Also included are halogenated aromatic hydrocarbons suchas'chlorobenzene, dichlorobenzenes, bromobenzene, fiuoro-. benzene,iodobenzene, 2-chloronaphthalene, orthochlorotoluene, parachlorotoluene,etc.

The alkylating reagent employed in our process is an olefinichydrocarbon containing at least three carbon atoms per molecule, or afunctional equivalent thereof under the alkylation reaction conditionsin the presence of PFs catalyst. By the term olefin-acting compound asused herein, we intend to define olefins and compounds which functionlike olefins under the reaction conditions, i. e. they react with thearomatic compounds to substitute therein a group containing at leastthree carbon atoms. By way of example, we may employ as alkylatingagents various monoolefinic hydrocarbons and mixtures thereof,specifically propylene, l-butene, Z-butene, isobutylene, l-pentene,2-pentene, B-methylbutene, 2- methylbutene, various hexenes, heptenes,octenes, l-dodecene; mixtures of isomeric dodecenes derived from thepolymerization of isobutylenes or isobutylene-n-butenes, or frompropylene; cyclic monoolefinic hydrocarbons such as cyclopentene,various alkyl cyclopentenes, cyclohexene, alkyl cyclohexenes such asl-methyl cyclohexene, 4- methyl cyclohexene or the like; aromaticolefins such as styrene, alpha-methylstyrene, vinyl toluenes,chlorostyrenes and the like; (2,2,l)-bicycloheptene and alkylderivatives thereof, particularly the 4-alkyl(2,2,l)-bicycloheptenes,and the like. Especially desirable are olefins containing a terminalvinyl group, CH2.

We may also employ polyolefinic hydrocarbons containing at least threecarbon atoms per molecule as alkylating reagents, particularly thediolefinic hydrocarbons. Examples of conjugated diolefinic hydrocarbonswhich we may employ include 1,3-butadiene, isoprene, 2,3-dimethyl-l,3-butadiene, piperylene, 4-methyl-1,3-pentadiene,1,3-cyclohexadiene and the like. Examples of nonconjugated diolefinichydrocarbons which we may employ include 1,5-hexadiene, dipentene andrelated terpenic hydrocarbons, and the like.

Olefin-acting compounds which we may employ as alkylating agents includevarious halohydrocarbons, alcohols, ethers, alkyl sulfates or the likecontaining at least three carbon atoms in the alkylating group. We mayemploy such halohydrocarbons as alkyl and cycloalkyl halides, especiallychlorides or bromides, e. g., isopropyl chloride, n-propyl bromide,t-butylchloride, t-butyl fluoride, isopropyl fluoride, diisobutylenehydrochloride, cyclohexyl chloride, cyclohexyl fluoride,t-methylcyclopentyl chloride, benzyl chloride, 2,4-dichlorobenzylchloride, bis(chloromethyl)benzenes, allyl chloride, methallyl chloride,2,3-dichloro-2,3-dimethylbutane, 3-methyl-l,3- dichlorobutane and thelike.

Examples of alcohols which may be employed in this invention includeisopropyl, n-propyl, isobutyl, t-butyl, t-amyl, benzyl, cyclohexyl,t-methylcyclopentyl and t-octyl alcohols such as dimethylneopentylcarbinol. Various olefin-acting ethers may be employed as alkylating re-Example 1 -A- mixture of toluene and propylene in the molar ratio of 1.1to 1 was rocked inan autoclavewith 9P5 in the concentration of one 'molperceng based on propylene,

. at 25C. for 4.5 hours and then allowed to stand an a'dditional 'lhours. In detail; the following procedure was-used. The autoclave wasevacuated -a'nd 68 gp'of toluene: was introduced, following which l 69cc. F1 5 gas was charged-from a calibrated mercury displacement bulbizPropyle'ne was then pressured into the autoclave at roomtemperaturein'the initial quantity of 28 gf The initialtpressure wasabout 200p s.i. g.-' Upon completion of the reaction, the excess pressure invthe'autoc'lave was-bled olf;and 88.1 g. of a liquid product of slightlyreddish color-was removed therefrom, washedwithwater and dried withanhydrous calcium chloride. Upon' comtemperatures ranging upward from170 C., and its re- 'fractive' index (hi- Wa's 134902.

7 In the following table are recorded examples illustrating thealkylation of benzene by the appropriate alcohols to produceisopropylated, cyclohexylated and t-butylated V V In some of the ex: 7amples benzenediazonium hexafluorophosphate was egg benzenes in thepresence. of PFs.

ployed as catalyst." Reaction was efiected by placing 2.5 mols ofbenzene and 0.5 molof the alcohol in an Erlenmeyer flask. The: resultantsolution was. cooled in ,an

ice hath and approximately one-half mol' of phosphorus pentatluoride wasbubbled into the' solution, causing it to becom'ebrown'l: iThefiask wasthen .placed'onpa steam? plate and the reaction. mixture was refluxedfor 2 hours]: The reaction mixture was then allowed-to cool to roorntemperature. It separateddnto' two liquid layers, via. an upperorganic'layer and a lower aqueous layer, the

- latterbeing separated. and discarded. The. orgariiclayn was washedtwice with 50 ml. portions of 10% aqueous NaOH and twice WithS'O ml;portions of distilled water, following which it was driedforaboutlZhours with calcium chloride and then distilled from sodium. Whenbenzenediazonium hexafluorophosphate was employed, it

pletio'nofsthe reaction, the product contained 47.2 weight Thefollowing'data'were obtained.

TABLE 1 Benzene alkylation .CaHsR CsHlR: .Total :Time Percent 7 Ex.Alcohol ",(Hrs) Catalyst Yield, Yield,. of.

Mols Percfent Mols Percfent Theory 0 0 T e ry. eo y 6 rI N2PFLN .093 19.066 26 45' 2 PM .100 20 .042 17 '37 6 do v 2' tNzPFh" .-069 14 .061 24.38 Cyclohexyl. 2 'PF5 .198 40 1037 15 55 '8 .410. i 2' N2PF6- .1 62 32..058 23 .55

cent of alkylate containing 16 carbon atoms per-molecule; The cymenesyield was 21.7% of theoretical and 'the diisopropyltoluene yield was 20%of. theoretical.

' -Example 2 7 Into a B-necked flask fitted with a reflux-condenser wereplaced 200 g. oft-butylbenzene and 35 glof Z-pentene. T he flask wasalso provided with a thermometer and a'PFs inlet tube extendingbelow theliquid level. The mixture was heated to reflux-and PFa' gas-was slowlyintroduced from a calibrated mercury displacement 'bulb. @ver a 48 hourperiod the pot temperature increased fromfiifi" C. to 197 C. Atotal-of--6'l2cfibfPFs; gas Wasadded. .The solution turned dark andopaque: Product was cooled, 'water-wasned and .dr'iedz'over calciumchloride. The product weighed2l'd5 'g. Distillalation yi eIdedl-ZA g."ofmate'rial beiling 216243 :CL, n 1.4828; The yield of themon'o'alkylate, based on Z-pentene, is 12.7% of theoretical Y i'urpris'ingly, we'have found: that anhydrousy..liquid hydrogen fluorideexerts an :ifrhibitin g ietrect =in.;-.a;lkyla- .In the above table, Rrepresents the alkyl or;,cycloalkyl group whichwas'substituted in thebenzeneQnucleustviz.

7 In order todeterrnine the p'ositionlof thealk-yl, groups in thediallcylated benzenes,.-oxidation"of theside chains to well-knownbenzene derivativeswas usedf' The iso:

. meriophthalic acids or theirniethyl esters diiferwidely tion,particularly in the alkylation of toluene :by proin melting pointsh Twoand fivertenths grains of .diisc-- propyl lbeuzene were r-iflixedwith300 ,ml. of 5 N nitric acid fori18 hours. .A 77% yield of phthalic.acidwas obtained; After recrystallization from hot; water .and drying,the acid fsublirned without. melting above '300 f indicatingterephthalicacid This acid..was' heated with absolute methanol'in 'the presence oflqrydrogen clilor'-ide. On cooling, a mass of White. crystals separatedin the form'pf thin plates 'Ihe-crystalsmelted at 1412;, in:

dicatingthe dimethylrester ofterephthalic acidgThere wasnoindication'ofjs'ophthalic ester; A-separate-sample of the acid"was'atested- -f or orthophthalie acid by conver} sion to fluorescein(S. P. Mulliken, The Identification of Pure Organic Compounds, vol. I,pp. 84-5). The test indicated the presence of the ortho isomer but invery small quantity. The strongest test was given by the phthalic acidderived from the diisopropyl compound. The structures of the di-t-butyland dicyclohexyl compounds were determined by oxidation with chromicacid, and 86% and 72% of terephthalic acid was obtained.

This was identified as before.

In Table 3 are presented data obtained in examples of the alkylation ofbenzene with isopropyl alcohol, characterized chiefly by the employmentof relatively small proportions of PFs, based on the alcohol, ascompared izvith the examples of Table 1. The alkylations of Table 3 werecarried out in glass apparatus at atmospheric pressure, employing PFsgas derived from the thermal deco position of benzene-diazoniumhexafluorophosphate i an autoclave at 120l25 C. The PF5 and nitrogengases which were formed were bubbled through the reaction mixturecontained in a flask cooled in an ice bath. Upon absorption of PR; inthe reaction mixture it changed from colorless to a canary yellow colorand two liquid layers formed. The reaction mixture was refluxedthereafter for one hour. The reaction mixture Was then cooled to roomtemperature, the lower aqueous layer was discarded and the upperhydrocarbon layer was washed twice with aqueous sodium hydroxide andthen with water. The hydrocarbon products were then dried over anhydrouscalcium chloride and distilled from sodium.

TABLE 3 6 the 1,2,4-isomer. The tetraisopropylbenzene of Example 10 wasfound to melt at 117.5 to 118.5 C., indicating the l,2,4,5-isorner.

In Table 4 are presented data obtained in examples in which PF5 gas wasemployed as a catalyst under pressure with isopropanol, isopropylchloride and propylene for the alkylation of benzene and toluene. Inthese examples the PF5 was free of nitrogen,

The procedure employed in performing Example 15 is described in detailsince it is typical of the procedure employed in the other examples ofTable 4. The reactor was a 250 cc. stainless steel autoclave providedwith a magnetically-actuated stirrup-type stirrer (a commercialMagne-Dash reactor). It was pressure-tested with nitrogen, thenevacuated and 78 g. of reagent grade benzene and 20 g. of isopropanolwere introduced. The autoclave was then heated to 150 C. and PFs from aweighed sausage bomb was added over a 2.5 hour period, more being addedas the pressure dropped. A total of 19 g. of PFs was added and themaximum pressure was 500 p. s. i. g. at 150 C. Stirring of the reactionmixture was stopped after 2.5 hours and the autoclave was allowed tocool. The autoclave was opened and the product was transferred to aseparatory funnel. The lower aqueous layer was separated and discarded.The upper hydrocarbon layer was Washed twice with 50 cc, each of aqueous 10% NaOH solution and twice with water. The hydrocarbon product wasdried over calcium chloride and, weighed 71.2 g. The product wasdistilled from Alkylation of aromatic hydrocarbons with isopropanolusing PFs gas Molar Reaction Alkylate, Percent Theor. Yield Total Ex.Me] Ratio, Ratio, Period, Alkylate,

Aromatic/Alcohol Pf5/A1Clh0l Hrs. Percent CaH5R COH4R: CuHaRa C HzR4Theory (CaHo) 5/1 0. 6 35. 7 17. 3 12. 2 l5. 6 80. 8 (CaHa) 3/1 0. 52 531. 8 l 17. 3 12. 7 30. 9 92. 7 (CuHu) 2/1 0. 59 8 25. 5 14. 5 b 53 93.0(05111) 1/1 0. 59 2 24. 2 18. 5 12. 2 35. 8 90. 7 (Cumene) 5/1 0. 45 2 I25. 4 19. 2 15. 1 59. 7 (Toluene) 5/1 0. 45 2 48. 0 15. O 18. 0 81. 0

I Largely para-diisopropylbenzene. b Based on triisopropylbenzene.Ortho:meta:para=2:1:1.

Examples 9 to 12 show that decreasing the ratio of sodium using a 3-foothigh, %-inch diameter Stedman benzene to alcohol has little elfect onthe yield of diisopacked still. Distillation of products gave:

propylbenzene. The yield of monoisopropylbenzene is reduced as the ratiois decreased and higher yields of Grams Presslge, the polyalkylatedbenzenes are attained. Alkylation of g toluene and cumene withisopropanol in Examples 13 and 14, respectively, gave higher Yields ofthe dialkyliftfifilfiarsaun'ai: :3 i213 i ifrIIIIIIIII Z2333 benzeneproducts. Diisopropylbpgzeneun 60.8 T triisopropylbenzene of Example 10Was f01 1nd t0 gg if flgfff lffi fi Z; i{ f boil at C. at 20 mm. Hg, 111.4910, indicating TABLE 4 Alkylatz'on of aromatics under pressure usingPF5 gas Alkylate, Percent Theor. Molar Ratio, Aromatic/AlkylatingMolarRatio, Temp., Press, Reaction Ex. Agent PF5/Alkylat- O. p. s. 1. g.Penod,

ing Agent Hrs. G0H5R O6H4R2 Poly- Total alkylate (CnHs) 3/1(Isopropanol) 0. 45 500 2. 5 45. s 18.9 n 15. 6 so. 3(C6Hfl)3/1(ISOPTOP3HOD 0.5 24 350 24.0 71.4 21.5 92.9(CrHa)3/1(Isopr0pylchlon e) 0.59 142 525 3.0 50.0 29.0 =14.7 03.1(Toluene) 5/1 (Propene) 0.05 24 200 1.0 s 40.0 d 49.3 89.3

H Based on tetraisopropylbenzene. b Largely para-.

B 60% orthu; 20% meta; 20% para. 6 Based on diisopropyltoluene.

that a much higher yield of isopropylbenzene was ob .tained at roomtemperature and a'r'elatively long reaction period than at theconditions of'high temperatureand relatively short reaction period.

. Substitution of .isopropyl chloride for isopropyl alcoholin the'alkylation of benzene in an autoclave at elevated temperature and.pressure gave higher yields; of mono and diisopropylbenzenes as: shownby Example 17; This reaction may. be eifected with much smalleramountsof PF but it was carried out with this much PF-s to compare it withalkylations using alcohols. position was preferred in,dialkylation,possibly because of steric as well as electronicefiects.

.In Example 18 the alkylation of toluene with propylene proceeded atroom temperature (and 200 p. s. i. g.) using only a small amount of PFs.the steric' effect of'a methyl group in the aromatic feed stock is muchsmaller than that'of an isopropyl' group since the predominantdialkylbenzene was the ortho isomer. 7 V

In the alkylation of benzene by isopropanol in the presence of 0.5 to 1"mol of benzenediazonium hexafiuorophosphate per mol of isopropanol, theformation of substantial yields of diphenyl, amounting to about onethirdof the theoretical maximum, was noted in some instances. Apparently,decomposition of the hexafluorophosphate in the presence of benzene andPFs occurs to form nitrogen, HF and diphenyl.

Chemical and physical tests we'reusecl to determine the isomerdistribution of the diisopropylbenzene s of Examples 10, 13 and 17.These were'oxidized withl SN 'nitric acid for 16-18 hours at refluxtemperature. Oxidation yields of 75 to 82% were obtained. .'The phthalic:acids sublimed above 300 C.- Only a faint test for 'orthophthalicacidwas obtained by means of the fluoi rescein test. The acids wereconverted to the dirnethyl ester by reaction with absolute methanol andanhydrous HCl during one hour at reflux temperature. 'White plates ofthe dimethyl ester were obtained which melted at 139440 C. indicatingthe para isomer, dimethyl terephthalate. Thus the'strueture of theoriginal hydro- .carbon was predominantly para-diisopropylbenzene.

Although the specificexamples illustrate certain facets of ourinvention, it will be understood that it is more broadly applicable. Thealkylation may be conducted at temperatures between about C. and about150 C., the most desirable temperature or. temperaturerangeemployed inany specific instance beingreadily determined by simple small-scaleexperiment. The pressure "can likewise be broadly varied as well as themolar ratios of the reactants and of catalyst to the reactants. The-reaction can be carried out in the presence of-inert-solvents or reactionmedia, usually in the presence of non-reactive Example 18 indicates thattion,products (resulting from the introduction of. more than onealkylgroup in the aromatic 'compoundcmployed as charging stock): arewnotdesired, the'ipolyalkylation products formedin the reaction may berecycled, in*continuousprocesses, orrnay; be charged in proportions upto about the equilibrium proportion in batch. .a'lkylation procedures.The usual :equipment-and operating methods I which are known in thealkylation artand in related arts of effecting chemical reactions andprocesses may be employed for the purposes of our invention: andespecially forits adaptation to large scale usage.

Having. thus described our invention, what we claim is: f 3 1.Anqalkylationv process-which comprises contacting;

aniaromatic-compound having at leastonefialkylatablet nuclear carbonatom with an olefin-acting compound cointaining at least three carbonatoms in .the. alkylatigng group withPFs under alkylationreactiontconditionsfia The para 2. The process of claim lwherein said:aromatic coh pound is" an aromatic-hydrocarbon.

3. An alkylation process which :comprises contacting an aromatichydrocarbonih'aving at, least .one alkylatable nuclear carbon'atom witha monoolefinic hydrocarbon containingat least three' carbon.atomspermolecule and WithPFs underalkylation reaction. conditions. a

Y 4. The process of claim 3 wherein'saidmonoolefinic hydrocarboncontains azterminal vinyl group.

5. The process of -claim 3 wherein said aromatic hydrocarbon is benzeneandsaid'monoolefinic hydrocarbon is propylene.

6. The process of claim 3 wherein said aromatic hydrocarbon is tolueneand said monoolefinic hydrocarbon is propylene. V e

. .7.. The process ,of claim 3 wherein-said aromatic hy drocarbon iscumene and said monoolefinic hydrocarbon is propylene V V H 8. Theprocess of claim 3 wherein said aromatic hydrocarbon: ist-butylbenzeneand saidmonoolefinic hydro- .carbon is isobutylenehydrocarbons such as liquid paraffins and/or cyclo" per part by weightof the aromatic compound employed 7 as a .feed stock. Inthoseinstancesin which polyalkylw a k tm q s s .wh s 9 P i wad an aromatic hydrocarbonhaving at least one alkylatable nuclear. carbon atom with an alcoholhaving at least three carbOn-atomsper molecule and-with P-Fs underalkylation reaction conditions; j W 1;; i V

10;:alkylation process which comprisescontacting an' aromatichydrocarbonhavingat least one alkylatable nuclear carbon atom with ahal'ohydrocarbon: having at least three carbon atoms per molecule[andwith PFsunder alkylation reaction conditions.

-11.. Analkylation process which comprises reacting a secondaryaleohol'containing' at leastlthree carbon' atoms per moleculeand atleast an equimolarproportion of an aromatic compound having at least onealkylatable nuclear carbon atom WithPFs in a proportion of at leastabout 30 mol percent,based onsaid alcohol, at-a ternperature suflicient'to efiect' 'alkylation.

References Cited in the file of this patent UNITED STATES PATENTS1,933,434 Hofmann et a1. Oct. 31, 1933 2,430,660 Axe Nov. 11, 19472,584,102 Mavity- Feb. 5. 1952 2,683,763 Lien et: al. 2 July 13 19542,683,764 Lien et al. Julyl3j1954

1. AN ALKYLATION PROCESS WHICH COMPRISES CONTACTING AN AROMATIC COMPOUNDHAVING AT LEAST ONE ALKYLATABLE NUCLEAR CARBON ATOM WITH ANOLEFIN-ACTING COMPOUND CONTAINING AT LEAST THREE CARBON ATOMS IN THEALKYLATING GROUP WITH PF6 UNDER ALKYLATION REACTION CONDITIONS.